Modifying cellulosic fabric with dicarboxylic acids to impart water-dispersibility

ABSTRACT

CELLULOSE HALF-ACID ESTERS ARE PREPARED BY IMPREGNATING CELLULOSIC MATERIAL WITH A CONCENTRATED AQUEOUS SOLUTION OF AN ORGANIC DICARBOXYLIC ACID ANHYDRIDE AND AMMONIA, HEATING THE IMPREGNATED CELLULOSE MATERIAL T 160* TO 200*C. FOR ABOUT 10 TO 60 SECONDS UNTIL THE DESIRED ESTER SUBSITUTION HAS OCCURRED, WASHING THE ESTERIFIED CELLULOSE, AND NEUTRALIZING THE FREE CARBOXYL RADICALS WITH A SOLUTION CONTAINING METAL IONS. THE EXAMPLES ILLUSTRATE THE EFFECT OF VARYING THE TEMPERATURE AND TIME ON THE DEGREE OF SUBSTITUTION OBTAINED WITH SUCCINIC, PHITHALIC AND MALEIC ANHYDRIDES. CELLULOSIC FIBERS CAN BE MODIFIED SO THAT FABRICS WILL DISPERSE READILY IN WATER.

US. Cl. 8-120 United States Patent 3,671,184 MODIFYING CELLULOSIC FABRIC WITH DICAR- BOXYLIC ACIDS TO IMPART WATER-DISPERS- IBILITY John Anthony Cuculo, Raleigh, N.C., assignor to E. I. du Pont de Nemonrs and Company, Wilmington, Del. No Drawing. Filed May 26, 1969, Ser. No. 827,975 Int. Cl. D06m 13/20; A61f 13/16 4 Claims ABSTRACT OF THE DISCLOSURE Cellulose half-acid esters are prepared by impregnating cellulosic material with a concentrated aqueous solution of an organic dicarboxylic acid anhydride and ammonia, heating the impregnated cellulose material at 160 to 210 C. for about 10 to 60 seconds until the desired ester substitution has occurred, washing the esterified cellulose, and neutralizing the free carboxyl radicals with a solution containing metal ions. The examples illustrate the effect of varying the temperature and time on the degree of substitution obtained with succinic, phthalic and maleic anhydrides. Cellulosic fibers can be modified so that fabrics will disperse readily in water.

FIELD OF INVENTION This invention relates to a process for reacting organic dicarboxylic acid anhydrides with cellulosic materials, and is more particularly concerned with modifying cellulosic fibers of fabric materials to make them dispersible in merely turbulent water, i.e., without the use of high energy equipment such as paper heaters or paper mills.

When diapers, or fabrics used for other sanitary purposes, are to be disposed of without washing for reuse, it is desirable that they be dispersible in water so that they can be flushed away as sewage. This can be accomplished by chemical modification of fibers to make the surfaces slippery when wet. Fabrics composed of such fibers will come apart when agitated in water, and the dispersed fibers can be flushed away Without clogging sewage systems. The present invention provides an economical process for substituting suitable hydrophilic radicals on the surface of cellulosic fibers. The degree of substitution can be controlled so that fabrics of the modified fibers will have adequate strength when dry or wet with salt solutions, but will be dispersible in turbulent city water.

SUMMARY OF THE INVENTION In the process of the present invention, cellulosic material is reacted with a substantially saturated aqueous solution of a partial ammonium salt of an organic dicarboxylic acid by heating within the temperature range of 160 to 210 C. to form a reaction product weighing, after washing to remove excess reactants and drying, about 10% 6 40% more than the original dry cellulosic material. It is believed that the dicarboxylic acid has reacted with cellulose hydroxyl groups to form half esters of the dicarboxylic acid. The extent of reaction with cellulose hydroxyl groups may be stated in terms of the degree of substitution (D.S.) which is the ratio of the moles of acid esterified to the moles of C H O in the cellulosic material, the maximum D.S. being 3.0. When modifying cellulosic fibers to make fabrics of them dispersible, the reaction is preferably conducted so as to provide a D.S. of about 0.15 to about 0.40.

A preferred treatment for fabrics of cellulosic fibers is to dissolve an organic dicarboxylic acid anhydride in water containing sufficient ammonium hydroxide to provide 1 to about 1.5 moles of ammonia per mole of an- Patented June 20, 1972 "ice hydride, impregnate the fabric with sufficient solution to provide 1.5 to 20 times the amount of acid to be reacted with the cellulose, heat the fabric within the temperature range of 160 to 210 C. until the cellulosic fibers have a D.S. of about 0.15 to about 0.40, wash the fabric to remove excess reactants, and neutralize the free carboxylic acid groups with a buffered alkaline solution containing deswelling salt to form the sodium salt of the acid groups.

The fabric may be soaked in a substantially saturated solution of the organic dicarboxylic acid anhydride and ammonium hydroxide until the fabric picks up about 1 to 3 times its weight of the solution. The solution may contain a minor amount of esterification catalyst. Alternatively, the fabric may be wet with ammonium hydroxide solution and then passed through molten acid anhydride to form a saturated solution in the fabric.

DETAILED DESCRIPTION Reactants Preferred dicarboxylic acids include succinic acid, maleic and ortho-phthalic acid as well as substitution products containing such groups as alkyl, alkyloxy, halogen, nitro, and hydroxyl. Suitable acids include itaconic acid, citraconic acid, and hydroxy ortho-phthalic acids.

The cellulosic material can be in any convenient form such as fibers, woven or knitted fabrics of the fibers, nonwoven fabrics, wood pulp, cotton linters, films, granules, or powders. Regenerated cellulose in the form of fibers is preferred. This includes all cellulose fibers formed from a solution such as viscose rayon, cuprammonium rayon, deacetylated cellulose acetate fibers, denitrated nitro-silk and the like. Fibers made from low-substituted cellulose derivatives such as hydroxy ethyl cellulose or methyl cellulose may also be used.

Reaction considerations The following discussion of process and examples will be in terms of cellulosic fibers, and more frequently fabrics of the fibers, although it will be understood that the comments also apply to other cellulosic materials, as powders, films, etc. Near-saturated solutions are preferred in order to keep the amount of water to be dried out to a minimum. Unless otherwise specified, all solution concentrations are expressed as percent by weight.

The reactant solution is conveniently prepared by mixing water and ammonium hydroxide and then dissolving the acid anhydride. The heat of solution and reaction will assist in dissolving the acid anhydride to the extent desired. External heat can be applied to keep the solution in solution. Temperatures of about C. are useful for acid anhydrides as succinic and maleic. Phthalic anhydrides require a higher temperature of about -85" C. to obtain the concentration required. Catalyst, if used, can be added after the anhydride is dissolved.

The reaction with some anhydrides proceeds at a satisfactory rate merely as the result of the application of heat and no catalyst is necessary. However, catalysts may be used if desired. Materials that have an effect in promoting the esterification include sulfamic acid, p-toluenesulfonic acid, zinc chloride, magnesium chloride, and the like.

When using a solution, fabric is soaked in the acid anhydride solution long enough to thoroughly wet it so it will retain the quantity of reagent desired. The term pick-up (i.e., weight of solution in the fabric/original dry weight of fabric) is used to indicate the amount of reagent applied. The pick-up desired will vary with the particular acid used, the concentration of the acid, and the extent of reaction. In general, the fabric should contain from 1.5 to 20 or more times the theoretical amount of acid for the extent of reaction desired. Pick-ups of from about 1 to 3 are conveniently used.

Excess solution picked up in the soaking process is removed by centrifuging or by the application of pressure. In the preferred continuous process, using a warp sheet or pre-formed fabric, the fibers are run through a dip tank of solution, and then between conventional squeeze rolls adjusted to leave the desired amount of liquid on the fibers. Alternatively, the exact amount of solution needed is applied directly to the moving warp sheet or fabric by means of a conventional padder. In this case no excess solution need be removed.

The fibers that have been treated with the required amount of acid reagent solution may be dried slowly at room temperature or slightly elevated temperature. In the interest of speed and economy it is preferred to dry the fibers as part of the high-temperature reaction operation while maintaining a high humidity atmosphere during the drying stage of the process.

The heating of the fibers to bring about reaction can be carried out by any known means that allows reasonably careful control of the time and temperature of reaction. Hot circulating air ovens, or, in the case where sheet materials are used, heated rolls may be used. In the preferred process, using a pre-formed entangled-fiber nonwoven fabric, a tenter frame provides a convenient means for holding the fabric flat and at the desired dimensions while exposing it to a controlled flow of hot air to drive off water and bring about the esterification reaction.

The process can also be carried out by passing a fabric wet with ammonium hydroxide solution through a bath of molten acid anhydride and then heating. This is especially useful with the lower melting anhydrides such as maleic.

Purification and after treatments The fibers or fabric obtained at the end of the hightemperature reaction are contaminated with excess acid anhydride, small amounts of the corresponding dibasic acid, and traces of various decomposition products. These impurities are easily removed by means of a Water wash. Since the half ester formed in the reaction is in the free acid form, or ammonium salt form to a small extent, the fibers of the more preferred products (D8. of 0.2 to 0.3) are low-swelling and no damage is sustained by the fibers or fabric in this treatment.

The final washed fabric, whether arrived at by modifying pre-formed fabric or by forming fabric from premodified fibers, is next converted to the more useful highswelling form by treatment with a base, preferably a slightly alkaline buffer such as disodium phosphate to form the sodium salt of the acid groups. In order to prevent excessive swelling and possible solution or other damage in the alkaline medium the buffer may be mixed with a solution of a deswelling salt such as sodium sulfate. Other strongly ionizing salts such as ammonium sulfate or sodium citrate may also be used, but sodium sulfate appears to be the most effective and economical, and the most desirable as a minor residual solid in the final fabric. Suitable salts are discussed in US. Pat. No. 3,328,892 to Man dated July 4, 1967. In order to prevent stiffening or harshening during drying, the fabric is dried directly while still wet with the deswelling buffered salt solution. Mechanical working during drying helps to soften the fabric and remove excess free salt. If a salt-free final product is desired, it may be obtained in a softened form by extracting the buffered salt solution with aqueous alcohol or acetone, rinsing in dry alcohol or acetone, and then drying with heat. Alternatively, the use of salt may be minimized by neutralizing the free acid groups in the fabric with an aqueous alcohol solution of a buffer or dilute alkali, followed by an alcohol or acetone wash, and then drying with heat.

The following neutralization baths are used in the examples:

The ingredients are dissolved in water and the pH adjusted to the noted value by the addition of dilute base. The bleach is commercial sodium hypochlorite solution. Other agents can be added as desired.

Utility of the products In addition to the preferred utility already discussed, the products of the process are also useful in a number of other ways. They may be used as cation exchange mediums. The sodium or ammonium salt forms are soluble in dilute alkali and the solutions are useful in the formation of films and fibers. Fibers of the products may be treated with heavy metal ions such as copper ions to give increased resistance to mildew and decay. The moisture absorbency and dyeability of cellulosic materials such as cotton or rayon can be increased by modifying the fibers in accordance with this process.

Preparation of nonwoven fabric (A) Nonwoven fabrics of entangled fibers are conveniently made by treating a fibrous web with fine, closely-spaced, liquid streams issuing from orifices at high pressures as taught by British Pat. No. 1,088,376, published Oct. 25, 1967.

Typically a web of 1.0 ounce per square yard (34 grams per square meter or g./m. of 1.5 denier per filament (d.p.f.), 0.75 inch (1.9 cm.) long rayon staple, in a random array made by air deposition, is placed on a 24 x 24 mesh per inch (per 2.54- cm.) screen (16% open area) and passed at 6 yds./minute (5.5 m.p.m.) under 3 rows of water streams coming from orifices having an upper cylindrical section of 0.005 inch (0.13 mm.) diameter with a lower frustoconical section as an exit and spaced 40 per inch (per 2.54 cm.) at pressures of 400, 500 and 600 pounds per square inch (28, 35 and 42 kilograms per square centimeter, kg./cm. respectively, (all pressures are gauge). The orifices are about 12 mm. above the web. This strong, integral nonwoven fabric (A) having a pattern of apertures is used in the examples. The fabric has a strip tensile strength of 3.3 lb./ in. (590 g./crn.) when dry, a Wet coefficient of friction of 1.32 and when tested as defined below, substantially zero dispersibility and about 0.7-0.9 single layer absorbency.

TEST METHODS Dispersi'bility The dispersibility is determined in a 250 ml. filter flask having an added side arm at the bottom of the conical wall and containing a magnetically rotated bar. The bar is 3.8 cm. long by 8 mm. in diameter, weighs 11.73 grams and is rotated at 500 revolutions per minute. A 3 x 3-inch sample of fabric is folded in half and inserted under the surface of the water (at the top side arm). Tap Water at about 25 C. is added through the bottom tube at a rate of 0.70 liters/minute for a period of 2 minutes. The efiluent liquid from the upper side arm is filtered and the residue dried to constant weight at C. to give the weight of fibers dispersed. The contents of the filter flask are filtered after the test and dried to yield the weight of undispersed fibers. The percent dispersibility is equal to 100 times the weight of fibers dispersed divided by the total weight of fibers recovered. Conventional toilet tissues have a dispersibility of 7% in this test.

In addition to the above quantitative result, the notes under dispersibility also include a visual estimate of the percent of fabric that has dispersed in 2 minutes or the time (less than 2 minutes) when the fabric has completely dispersed.

Nonwoven fabrics processed by this invention having a weighed dispersibility of from 20% to about 100% or a visual dispersibility from about 80% to about 100% are flushable in normal household toilets in the form of diapers. Those fabrics having dispersibilities as low as 4% (by weight) or (visual) may be dispersed in water with relatively mild agitation.

The degree of substitution of a cellulose product of this invention is calculated from carboxyl group analysis. A portion of a sample is treated with sulfuric acid to insure conversion to the carboxylic acid form, washed free of acid, and then dried. A weighed portion of the dried product is shaken with a measured amount of calcium acetate solution. The acetic acid liberated is back titrated with 0.1 N NaOH and the percent of acid groups is calculated.

Single layer absorbency The single layer (designated SL) absorbency method has been devised to measure fiber absorbency in the fabric state and to minimize interstitial water. A 3 in. x 3 in. (7.6 x 7.6 cm.) sample in a IOO-mesh screen basket is immersed for 1 minute in 150 ml. of a 0.1% aqueous NaCl solution and the basket is then dipped in and out of the solution 5 times and drained for seconds. The procedure is repeated in a fresh salt solution and the sample soaked for 5 minutes before draining the basket for 30 seconds. The wet sample is dropped from the basket onto a dry blotter and immediately dropped from the first blotter to a second dry blotter and covered with another dry blotter. The 2 blotters (5 x 5 in.) and intermediate sample are covered with a 5 in. x 5 in. aluminum plate and a weight added on top to give a total weight for the weight and plate of 3 kg. The sample is pressed at the 3 kg. pressure for 5 minutes and weighed immediately. The sample is dried for 2 hours in a hot air oven at 125 C., cooled in a desiccator and weighed immediately. The SL absorption is obtained by dividing (pressed wet weight minus dry weight) by the dry (final) weight to yield grams of solution/grams of dry fabric.

If the SL absorbency is less than 1.0 g./g., the determination should be repeated using blotters that have been slightly dampened (about 0.2 g./ g. of dry blotter) with a fine spray of the salt solution. Such a procedure avoids a false reading caused by some of the solution from the fibers (as well as interstitial) being absorbed by the dry blotters.

Conversely, if the blotters appeal to be fully soaked, the procedure should be repeated with the addition of a paper towel on the outside face of each blotter as all of the interstitial solution is not removed otherwise.

Strip tensile strength and elongations are measured on an Instron testing machine using a 2-inch (5.0 cm.) length between jaws of a 1.0 inch (2.54 cm.) wide sample and elongating at 50% per minute. For wet tensile strengths, samples are soaked in the appropriate liquid for 5 minutes at room temperature and then clamped in the tester and broken in air.

EXAMPLE I This example illustrates a continuous process for the chemical modification of a rayon nonwoven fabric.

The nonwoven rayon fabric (A) described previously, is passed through a tank containing a solution at about 60 C. of 40% succinic anhydride and the stoichiometric amount of ammonia (from NH OH) needed for the monoammonium salt. The fabric is squeezed by a pair of rubber-covered rolls to a pick-up of 1.7. The wet fabric is continuously passed through a commercial fabric oven (Benz) where it is exposed to opposed jets of air at 205 C. for a period of about 57 seconds to give brown colored fabrics. The baked fabric is washed With tap water and then neutralized and bleached (to an off-white color) in neutralization bath F and air dried. The properties of the product are as follows:

Strip tensile strength:

Dry lb./in.: 4.5 (G./cm.): (800.) In tap water lb./in.: 0.02 (G./cm.): (3.6) In 1% NaCl lb./in.: 0.07 (G./cm.): (12.5) Dispersibility:

Percent fibers recovered: 35. Percent fabric dispersed: 100% in 7 seconds Coefficient of friction, wet: 0.52 SL absorbency (g. sol./ g. fabric): 3.01 D.S.: 0.26

Diapers are assembled with a layer of the product, wood fluff, crepe tissue Wadding, wood fluff and the product in order. The outer layers of the product fabric are 11 x 14 inch (28 x 35 cm.) and the inner core of wood fluff and crepe tissue are 5 x 12 inch (12.7 x 30 cm.). The two fabric layers are glued together around the edges of the core with about 3 mm. spots of a water-soluble adhesive spaced about 5 cm. apart. The diapers can be flushed in a home-type toilet with tap water (200 ppm. hardness) after 3 to 5 dips without causing the toilet-bowl to overflow or lodging on wire hooks located in the exit pipe of the toilet.

Repetition of the above process using a pick-up of 1.6 gives a modified fabric with a dispersibility of 14%.

EXAMPLE 2 This example shows the effect of the concentration of succinic anhydride solutions on the process.

Solutions are prepared by mixing water with ammonium hydroxide (1 mole of NH /rnole of anhydride) and then adding the succinic anhydride slowly. No external heat is required to effect complete solution but the solutions are heated to maintain them at about 50 C. while using.

Preweighed, 5 x S-inch (12.7 x 20 cm.) portions of the entangled rayon nonwoven fabric are immersed in the reactant solution for about 1 minute, removed and squeezed and/or pressed on blotters to a pick-up of 1.9 (i.e., 1.9 grams of solution/ gram of original dry fabric). The wet fabric is clipped between 2 Teflon screens which are then hung in a stainless steel box with slots on the top and bottom in a circulating air oven adjusted to 205 C. A thermocouple is in contact with the fabric.

After heating for seconds, the fabric is removed washed with water, neutralized in bath E, blotted and air dried.

Results are given in Table I as items (a)-(e).

The as-baked products are strong both dry and wet and have a tan color.

The extent of reaction as judged by the dispersibility values increases with the concentration of the anhydride in the reactant solution.

EXAMPLE 3 This example shows the effect of an esterification catalyst on the reaction with succinic anhydride.

Preweighed 5.5 x 5.5 inch (1.4 x 14 cm.) portions of the entangled rayon nonwoven fabric are treated with an aqueous solution containing 50% succinic anhydride and 1 mole of NH /mole of anhydride to a pick-up of 1.9 (item (f) The wet fabrics are clipped to a stainless-steel screen and hung in a tube oven so that hot air enters the oven through a diffusing plate, passes through the fabric and exits from the oven. A thermocouple is in contact with the fabric. The oven temperature (205 C.) is measured by a thermocouple downstream of the fabric.

The procedure is repeated with the addition of sulfamic acid (2% of the weight of succinic anhydride) to the solution to make item (g).

The baked fabrics are Washed in water, neutralized sion of the sulfamic acid. After baking for 60 seconds it is washed and neutralized in bath A.

All items are strong in the as-baked state except (f). It is speculated that the lower tensile of item (f) is due to and bleached in bath A, blotted and air dried. Results are 5 an ihreaed degradation the Y T color of the given in Table I as items (f) and The asFbaked as-baked ltems increases with reaction time from an offfabrics are strong; Item (f) has a rather brown color and 3;? to brown An are bleached m the neutrahzanon item (g) an off-white color; both are bleached to a satis- EXAMPLE 6 factory White.

The increased extent of reaction using the catalyst is 10 T PP effect f temperature Wlth Small obvious from the dispersibility values of the products. varlatlfms m tlme on the Yeactlon between rayon and phthalic anhydride. EXAMPLE 4 The procedure of Example 5 using sulfamic acid as a catalyst is followed with oven temperatures and times as This example shows the effect of time on the reaction given in Table II f items (g) (m) and using neutraliza between rayon and SLICCIHIC anhydfldetion bath C. The solution for item (m) contains 36.6%

The procedure of item (g) of Example 3 1s repeated h h 1i h d id with reaction times of 10 to 60 seconds to give items All as-baked fabrics are strong wet and dry and colored (h)-(m) as reported in Table I. The color of the as from tan to brown. All are bleached in the neutralization baked fabrics increases with the reaction time from an bath.

TABLE II Dispelsibility Temperature, C. Reaction Neutral- Visual, 8.1,.

time, Maximum ization Fibers, percent/ absorb- Item seconds Oven on fabric bath percent seconds D. ency 60 205 202 A 5 10 205 164 B 4 20 205 194 B 13 205 200202 B 205 204 B 30 205 200 B 05 50 190 184 o 5 50 195 190 o 5 50 200 103 c 10 40 200 185 o 4 50 205 201 o 40 40 205 201 0 22 30 205 190201 0 42 100/20 No catalyst. t Pick-up 1.8.

NorE.-Reactant solution 36.3% phthalic anhydride, 1.5 moles NHgalmole of anhydride and 2% (based on anhydride) of suli'amic acid as a catalyst; pick-up 1.

off-white for item (h) to a dark brown for item (In). All are satisfactorily bleached in the neutralization bath.

Item (m) has a tensile strength in distilled water of 0025/0015 (MD/XD) lb./in. (4.5/2.7 g./cm.) and a TABLE I Reaetant solution Dispersibillty Tempera- Per- Reaction ture, 0., Neutral- Visual,

Anhydride, cent 1 time, maximum izatlon Percent percent/ Item percent catalyst seconds on fabric bath fibers seconds D.S

20 0 00 192 E 5 15/120 25 0 90 195 E 12 25/120 30 0 90 191 E 33 -90/120 40 0 90 186 E 41 -90/120 50 0 90 100 E (if) 100/7 50 0 60 200 A 15 -50/120 50 2 60 202 A 100/10 50 2 10 158 A 2 10/l20 0. 073 50 2 20 192 A 5 -10/l20 0. 17 50 2 30 108 A 19 45/120 0. 26 50 2 40 192 A 38 100/10 0.28 50 2 50 204 A 38 100/7 0.31 50 2 204 A 32 100/5 0. 30

1 Percent (based on anhydride) of sulfamic acid.

Nora-205 0. even used {for all items; reactant solution contains 1 mole Nils/111010 of anhydride; pick-up 1.9 [01 all.

EXAMPLE 5 This example shows the effect of reaction time on the reaction between phthalic anhydride and rayon.

A solution is made by dissolving 36.3% orthophthalic anhydride in a mixture of water and ammonium hydroxide that gives 1.5 moles NH mole of anhydride. Sulfamic acid (2% of the weight of the anhydride) is added. The extra 0.5 mole of NH is used to help dissolve the anhydride. The solutions are kept at about -90 C. to maintain complete solution.

Fabrics are treated with the solution to a pick-up of 1.9 and baked in the oven of Example 3 at 205 C. for different times of from 10 to 60 seconds. The baked fabrics are washed in water, neutralized in bath B, blotted and air dried to give items (b)(f) of Table II.

Item (a) of Table II is made as above with the omisfabric weight (including salt) of about 1.4 oz./yd. (47

EXAMPLE 7 This example shows the effect of temperature on the reaction between rayon and maleic anhydride.

The reactant solution is a 44.4% aqueous solution of maleic anhydride containing 1 mole of ammonia/mole of anhydride to which has been added sulfamic acid (2% of the weight of the anhydride). The solution is kept at about C. to keep it clear.

Portions of the entangled rayon nonwoven fabric are treated with the solution to a pick-up of 1.9 and baked in the oven of Example 3 at times and temperatures as given in Table III. Items (a)(c) are neutralized in bath C and items (d)-(e) are neutralized in bath D. The 2 baths are the same except for the inclusion of a bleaching agent in bath C.

Item (a) is made without sulfamic acid in the reactant solution.

All products are strong in the as-baked state, wet and dry, and are colored from off-white or yellow to light tan before bleaching.

TABLE III Dispersibility Temperature, C. S.L. Reaction N eutral- Visual, absorbtime, Maximum ization Fibers, percent] ency, Item seconds Oven on fabric bath percent seconds D.S. g./g

8. 30 205 194 0 6 b 10 205 166 c 13 c 30 205 190 c 11 d 30 190 180 D 13 e 30 180 171 D 34 r 30 170 161 D 21 g 30 165 160 D 13 1 No catalyst used.

No'rE.Reactant solution 44.4% maleic anhydride, 1 mole NHa/mole of anhydride and 2% (based on anhydride) 0t sulfamic acid as a catalyst. pick-up 1.9 g./g.

succinic acid, maleic acid and ortho-phthalic acid with 25 fabric of cellulosic fibers, the improvement for providing a product dispersible in turbulent water which comprises impregnating nonwoven fabric of entangled cellulosic fibers with a solution of 1.5 to 20 times the amount of the dicarboxylic acid to be reacted with the cellulose, dissolved in water containing 1 to about 1.5 moles of ammonia per mole of acid, heating the impregnated fabric within the temperature range of 160 to 210 C. until the cellulosic fibers have a degree of substitution of about 0.15 to about 0 .40, washing the fabric to remove excess reactants, and immersing the treated fabric in a buttered alkaline solution containing a deswelling salt to form the sodium salt of acid groups substituted on the cellulose.

2. A process as defined in claim 1 wherein the dicarboxylic acid is succinic acid.

3. A process as defined in claim 1 wherein the dicarboxylic acid is maleic acid.

4. A process as defined in claim 1 wherein the dicarboxylic acid is ortho-phthalic acid.

References Cited UNITED STATES PATENTS 2,358,387 9/ 1944 Dreyfus 8120 2,585,516 2/1952 Thomas 8-120 2,780,228 2/1957 Toney 8-120 3,526,048 9/1970 Rowland et al 8-120 OTHER REFERENCES St. Mard, American Dyestufi Reporter, vol. 50, No. 21, pp. 27-31 (1961).

Allen, Textile Research Journal, vol. 34, pp. 331-336 (1964).

Campbell et al., Textile Research Journal, vol. 35, pp. 260-270 (1965).

Rowland et al., Textile Research Journal, vol. 37, pp. 933-941 (1967).

GEORGE F. LESMES, Primary Examiner J. CANNON, Assistant Examiner U.S. Cl. X.R. 

